Sewage pump station

Abstract: The invention concerns a sewage pump station (1) with submersible pumps (8) to be lowered and raised along guides (15). In order to decrease the risk that the connection parts of the pumps (8) should disturb the flow within the pump station (1), the bottom (3) of the latter is designed with a slope (7) having a recess which accommodates said parts.

Description: The invention concerns a pump station for municipal sewage water, which pump station includes one or several submersible pumps. A pump station of this type is provided with one or several inlets for sewage water and normally one outlet pipe connected to the pump outlets. An example is shown in the Swedish Patent No 366 013. The submersible pump unit is normally lowered into the water along guides so arranged that the pump unit in its lowered position with its outlet makes contact with the outlet pipe from the station. The pump unit must then seal against the outlet pipe without any bolt attachment or the like. For this purpose a so-called connection support is arranged at the bottom of the station and provided with a pipe part attached to the outlet pipe and having a flange against which a corresponding flange on the pump outlet makes contact. Normally the lower parts of the guides are attached to the connection support. The sewage water contains a lot of solid bodies such as sludge which is easily assembled on the tank bottom as sludge banks, rags and other elongated objects which may be wound around the pump unit and its connection parts. Sludge banks and rags are a hinderance to the circulation and may also clog the pump inlet. It is known practice to solve the problem with sludge banks in the tank by help of intermittently operating mixing devices of the type shown in the Swedish Patent No 8900 597-9. Another method is to install special machines which keep the water moving within the tank. Another method which is used to prevent sludge from collecting at the bottom of the tank is to design said bottom with steep slopes and then arrange the pump inlet at the lowest point, as shown in US-A-4,661,047. However, the problem with elongated objects that stick to the guides, the supports etc still remains. According to the invention a reduction of the problems mentioned above is obtained by help of the device stated in the claims. The invention is described more closely below with reference to the enclosed drawing which shows a side cut through a sewage pump station designed according to the invention. In the drawing 1 stands for a sewage pump station or a tank having wall 2 and bottom 3. 4 and 5 stand for an inlet and an outlet respectively for sewage water, 6 and 7 are bottom plates in the tank, 8 a submersible pump unit having inlet 9 and outlet 10 with a flange 11. 12 stands for a connection support having a pipe 13 with a flange 14. 15 finally, stands for guide bars. The pump station is fed by sewage water through one or several inlets 4 and the water leaves the tank through the pressure pipe 5. The pumping is carried out by the submersible pump unit 8 provided with inlet 9 and outlet 10. In order to diminish the risk for sludge banks to occur in the bottom of the tank, said bottom is designed with one or several steep sloping planes 6 and 7 and the pump inlet 9 being arranged near the intersection of the planes where most of the solid bodies are collected. The pump unit 8 is lowered in the normal way down to its operation position along the guide. The latter normally comprises two bars which are surrounded by claw formed openings at the outlet part 10 of the pump unit. The lower end of the guide is than so positioned that the outlet part 10 with its connection flange 11 makes contact with a corresponding flange 14 on the pipe 13. By a suitable dimensioning the pump outlet will now be sealingly attached to the pressure pipe 5 without the need for the two flanges being bolted together. Thanks to this arrangement the pump unit may be easily hoisted up along the guide for maintenance. As previously mentioned it often happens that elongate objects, rags etc, get stuck to the projecting parts within the pump station. According to the invention the connection support 12, a part of the outlet pipe 5 and the lower end of the guide are arranged below the sloping plane 7, which constitutes a part of the bottom of the tank. In this way the number of projecting parts within the tank is diminished considerably which means a better flow within the tank and less risk for elongated fibres and other pollutions being collected. The arrangement of the connection support etc below the sloping plane 7 can be obtained in different ways. If the bottom of the pump station and the sloping plane are made of concrete, a suitable designed recess is made during the casting, which recess is big enough to accommodate the connection support and its connection. If an existing pump station is redesigned by help of sloping planes made of sheet metal or plastics, an opening is provided in the sheet and the connection support is placed beneath. After the mounting of the pump unit the opening may in both cases be provided with a cover, a sheet metal, which can be arranged to accompany the pump unit when this is hoisted up for maintenance. The pump unit 8 is in its operation position so arranged, that the inlet is close to the bottom of the tank, e g, at the lower end of the sloping plane 7 or, if the bottom consists of several planes 6 and 7, at their intersection. In this way is secured that the pump inlet is positioned at the point where the heavy objects collect which means that these are easily pumped out thus eliminating the problems with sludge banks. The elevations of the planes are preferably 40 to 60° with reference to the horizontal plane. In order to further decrease the risk that pollution should occur and to facilitate the flow, a further development of the invention provides for the guide 15 being possible to release from its lower attachment in the connection support 12. When the pump unit 8 has reached its operation position, the guide is removed and is entirely kept above the water surface in the tank until the pump unit is going to be taken up for maintenance.

Claims: A pump station for sewage water comprising a tank (1) with a wall or walls (2) and a bottom (3) and provided with inlet (4) and outlet (5) for water, further one or several submersible pump units (8) to be lowered to their operating positions near the bottom of the tank along guides (15), the pump unit (8) in its operating position having its outlet (10) in contact with a pipe part (13) arranged on a connection support (12) and connected to the tank outlet (5), characterized in that the bottom of the tank is provided with at least one sloping plane (6), (7) provided with a recess accommodating the connection support (12) the pipe part (13), a part of the outlet pipe (5) and preferably the lower end of the guide (15), which all will be situated below the surface of the plane (7) and thereby not constitute any hinderance to the flow within the tank. A pump station according to claim 1, characterized in that the sloping planes (6), (7) are made of sheet metal or plastics, one of the planes (7) having an opening for the parts (12) and (13). A pump station according to claim 1, characterized in that the sloping planes (6) and (7) are made of concrete, one of the planes having a recess which accommodates the parts (12) and (13). A pump station according to claim 1, characterized in that the guide (15) is releasable from its attachment in the connection support (12) and is kept above the water surface when the pump operates in order not to disturb the flow in the tank.

Inventors: PETTERSSON NIL-ERIK, PETTERSSON, NIL-ERIK
Applicants: FLYGT AB ITT, ITT FLYGT AKTIEBOLAG
Application year: 1994
Main classification: E03F5
IPC codes: F04D29, E03F5